For example, with respect to edges of a bonnet, a trunk, a door, and a wheel housing of an automobile, a hemming process is carried out by which a flange that is erected on the edge of a panel is folded and bent inwardly of the panel. As such a hemming process, a roll hemming process can be offered, in which the panel is positioned and retained on a fixing mold, and then a flange of an end part on the panel is bent while a roller is pressed with respect to the flange. With such a roll hemming process (hereinafter referred to simply as a hemming process), taking into consideration the bending accuracy for bending a large angle, a process is performed that involves a plurality of steps including a preparatory bending (pre-hemming) step and a finishing bending (main hemming) step.
In this type of hemming process, a workpiece is set on a mold that is disposed in a dedicated space for performing a specified process, and a hemming roller, which is disposed on a working tool that is held on the distal end of a robot, is rolled along the flange. Accordingly, in this manner, the hemming process is carried out (see, for example, Japanese Laid-Open Patent Publication No. 2010-279980).
As disclosed in Japanese Laid-Open Patent Publication No. 2010-279980, a hemming roller and a guide roller are capable of being displaced in a first direction, and in a second direction that is perpendicular to the first direction. According to this structure, even if errors in the movement trajectory of the robot (deviations with respect to the regular movement trajectory during operation) occur, such errors can be absorbed by displacement actions in the first direction and the second direction. Consequently, the influence of errors in the movement trajectory being imparted to the hemming process can be suppressed, and the burden on the robot or the processing tool can be reduced.